The evaluation of regional cerebral blood flow has primarily involved the external monitoring of injected or inhaled radionuclides. Although these radionuclide techniques have proven useful, they all have certain basic limitations, such as limited spatial resolution, extracerebral and recirculation contamination, and the use of hematocrit corrected yet theoretically derived fixed partition coefficients. In order to overcome many of the above limitations we propose to study in detail the possible derivation of dynamic information from nonradioactive Xenon enhanced serial CT imaging. The main thrust of the proposed study is the comprehensive assessment of regional cerebral blood flow measurement from serial CT imaging during and after inhalation of non-radioactive (stable) Xenon gas. While the proposed study will be carried out with non-human primates (papio cynocephalus (anubis)), questions which concern possible future clinical use of such techniques will be addressed in detail. In this study we propose not only to develop, test and optimize a protocol for such clinical application, but also to compare the results to those obtained by other well established techniques. In addition, we propose to investigate the feasibility of generating a multilevel neuroanatomic map of local rates of cerebral blood flow and partition coefficients.